The "impulse to grow" is being recognized as a very interesting and important phenomenon in the study of infancy and childhood. The growth in utero seems to be divided into two well defined parts; that of the first six months, and that of the last three months. Of the first period, not so much is known, for the opportunities to study this growth are relatively few. The second period, that of the last three months in utero, has been rendered very important from the pediatric point of view, firstly, because there is great growth during this period, and secondly, because this period is unfortunately often spent outside, instead of inside the uterus. It has always been an interesting theme to know whether: